Organic luminescent materials that are used in organic EL elements have a problem that they are deteriorated by moisture, and thus the lifetimes thereof are shorten. Therefore, hygroscopic materials moisture getters) have been conventionally disposed so as to absorb moisture that remains in organic EL elements during the production of the elements or moisture that enters from outside.
Since moisture getters are required to rapidly absorb moisture, after sealing, barium oxide or strontium oxide, or calcium oxide having an enhanced moisture absorption speed is used. Furthermore, for example, as disclosed in Patent Literature 1, calcium oxide having an enhanced moisture absorption speed can be obtained by calcining calcium hydroxide under a reduced pressure condition.